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F Thoné

Publications and source records attributed to F Thoné.

36 records · Page 2Linked to original sources
PubMed1985

Sarcolemma-bound calcium. Its importance for cell viability.

We report the presence of a sarcolemma-associated Ca2+-pool in the intact myocardium and isolated ventricular myocytes of the rat. Ca2+-deposits, which are visualized in the electron microscope as 20 nm thick particles, could be demonstrated when fixation of the tissue was performed in the presence of high inorganic phosphate and most probably represent stable Ca2+-acidic phospholipid-phosphate complexes. Various pathophysiological conditions all leading to intracellular Ca2+-overload and compromising myocardial cell viability were imposed and the distribution of Ca2+ was assessed. It was found that in all these conditions cellular Ca2+-overload was preceded or at least accompanied by a loss of sarcolemma-associated Ca2+-deposits. It is concluded that this Ca2+, possibly bound to acidic phospholipids of the sarcolemmal bilayer, plays a role in the maintenance of sarcolemmal integrity. These cytological observations support a concept previously proposed by Langer and his group on the controlling role of membrane Ca2+ in the overall cellular Ca2+-homeostasis.

Animals↗
PubMed1984

Cardioprotective effects of mioflazine during 1 h normothermic global ischaemia in the canine heart.

The cardioprotective effects of mioflazine, a recently developed cardiovascular drug, were investigated in 41 anaesthetised open chest Beagle dogs subjected to 1 h normothermic global myocardial ischaemia. The severity of the model is evidenced by the finding that only one out of 20 control dogs could be weaned from extracorporeal bypass. Oral pretreatment with mioflazine (2.5 mg X kg-1) resulted in complete functional recovery in 17 out of 20 animals. Biochemical analysis of left ventricular biopsies taken before, during and after aortic cross clamping showed a preservation of purines and a better recovery of ATP, ATP/ADP X Pi ratio and energy charge (p less than 0.05) in the pretreated animals. Morphological and cytochemical assessment of the myocardium demonstrated that the ultrastructure of the sarcolemma and its calcium binding capacity is remarkably well preserved in the drug treated animals. These results indicate a strong cardioprotective effect of mioflazine. The biochemical, cytochemical and ultrastructural findings suggest an interaction of the drug with the sarcolemma.

Animals↗
PubMed1983

The role of calcium in cellular dysfunction.

In order to study the effects of substances with selective Ca2+ entry blocking properties which enhance the tolerance to ischemia by preventing a toxic calcium overload, attempts are made to localize calcium ultrastructurally. Under normoxic conditions, a mobile pool of Ca2+ is localized in synaptic vesicles and in mitochondria of brain cells; in mitochondria of cardiac, skeletal and vascular smooth muscle; and in the junctional SR of fast skeletal muscle. A plasmalemmabound pool of Ca2+ is present in cardiac and slow skeletal muscle. Ischemia or hypoxia induce marked shifts in calcium of both the mobile and the plasmalemma-bound pools. Cardiac and skeletal muscle mitochondria scavenge huge amounts of calcium, especially during the reperfusion period following prolonged circulatory arrest. The membrane-bound Ca2+ is lost under these conditions. In the hypoxic brain, the amount of intracellular calcium clearly parallels the degree of damage. Observations made on peripheral and brain blood vessels show that high amounts of precipitated Ca2+ cover the myofilaments upon induction of spasm. The antispasmodic effect of the selective Ca2+-entry blockers flunarizine and lidoflazine is morphologically characterized by the absence of Ca2+ over the myofilaments in muscle treated as such whereas the extracellular Ca2+ remained the same. This observation indicates that the entry of Ca2+ is blocked at the level of the plasma membrane. In the heart and brain these drugs preserve the structural integrity of the plasmalemma-surface coat complex and thereby protect the cells against the devastating consequences of cellular calcium overload.

Animals↗
PubMed1983

Cardioprotective effects of lidoflazine in extensive aorta-coronary bypass grafting.

The cardioprotective effects of lidoflazine, a calcium entry blocker, were tested in patients undergoing multiple aorta-coronary bypass grafting (at least four grafts). Intermittent aortic cross-clamping at 25 degrees to 28 degrees C was used. Mean cross-clamp time was 11 minutes for one distal anastomosis. Patients were randomized into three groups: a control group (I), a group (II) pretreated with 0.5 mg . kg-1 lidoflazine intravenously before cardiopulmonary bypass (CPB), and a group (III) pretreated with 1 mg . kg-1 lidoflazine intravenously. The following markers of ischemia are used: (1) adenosine triphosphate (ATP), creatine phosphate (CP) and glycogen determined in transmural left ventricular biopsy specimens taken at the beginning and end of CPB; (2) ultrastructure in a similar pair of specimens; and (3) hemodynamic recovery 15 minutes after cessation of CPB. At the end of the intervention, ATP decreased to 73% in Group I but remained unchanged in Groups II (98%) and III (88%). CP decreased to 82% in Group I and remained unaltered in Groups II (100%) and III (110%). Glycogen decreased in Group I (to 44%) and in Group II (78%) but remained unchanged in Group II (138%). Ultrastructural study showed better preservation of the glycocalyx and sarcolemma in Group III than in Group I. Left ventricular stroke work index remained unaltered after CPB in Group III but decreased in Groups I and II to about 60% of its initial value. Thus lidoflazine pretreatment protects the myocardium in a dose-dependent manner against deterioration of myocardial function and structure.

Adenosine Triphosphate↗
PubMed1981

St. Thomas cardioplegia versus topical cooling: ultrastructural and biochemical studies in humans.

Transmural left ventricular biopsies were studied from 28 patients undergoing cardiopulmonary bypass with anoxic cardiac arrest. The myocardium was protected by topical cooling (20 degrees C) (Group 1, 15 patients) or by cardioplegia with St. Thomas' solution (Group 2, 13 patients). Biopsies were taken at the start of bypass and 3 to 5 minutes after unclamping of the aorta. Mean cross-clamp time was not significantly different between the groups (50 minutes for Group 1 and 53 minutes for Group 2; p greater than 0.05). The ultrastructural changes induced by ischemia and subsequent reperfusion were almost exclusively related to the mitochondria. The degree of mitochondrial damage was evaluated by a semiquantitative analysis based on mitochondrial fine structure. The frequency of severe postischemic mitochondrial damage was significantly higher in Group 1 (20.1% versus 2.7% in Group 2; p less than 0.05). Biochemical analysis of the biopsies indicates that the myocardial concentration of creatine phosphate decreases by about 50% after topical cooling (p less than 0.05). With St. Thomas cardioplegia, no significant change in the tissue level of this high-energy phosphate takes place. The results show evidence of the superiority of the St. Thomas cardioplegia to topical cooling alone.

Adult↗
PubMed1980

Effects of flunarizine on the distribution of calcium in vascular smooth muscle.

Exposure of depolarized caudal artery preparations of the rat to various calcium concentrations evoked sustained contractions of the smooth muscle in a dose-dependent way. Flunarizine was shown to suppress this sustained muscle contraction. Experiments were undertaken to determine the subcellular site where flunarizine interferes with the calcium-induced contractile process. The subcellular distribution of calcium was assessed by electron microscopy, using a combined oxalate-pyroantimonate method. In depolarized strips precipitated calcium was mainly distributed over the contractile elements and the microvesicles lining the cell membrane. When flunarizine was added to the preparation, the precipitate was predominantly confined to the extracellular space, whereas only spotty precipitates were seen in mitochondria and sarcoplasmic reticulum. The myofibrils were almost free of deposits. Without previous depolarization, the smooth muscle cells demonstrated a moderate amount of precipitate over the mitochondria, nuclei, sarcoplasmic vesicles, plasmalemmal microvesicles and myofibrils. In these conditions neither the amount nor the intracellular distribution of the precipitate was influenced by the addition of flunarizine. These observations suggest that flunarizine interfers with the entry of calcium at the plasma membrane level, but only in conditions where the influx of the ion is stimulated.

Animals↗
PubMed1978

Alkaline phosphatase activity in human polymorphonuclear leukocytes.

Alkaline phosphatase has been localized ultracytochemically in PMN of man with normal and elevated levels of this enzyme. Contrary to guinea-pig PMN, no activity appears to be present in the specific granules. Instead, the plasma membrane and the membrane of the endocytic vacuoles show a strong staining. However, the demonstration of this activity depends on the preparatory procedure employed for PMN isolation. The use of dextran and Ficoll-Hypaque in the isolation procedure induces a marked increase in alkaline phosphatase staining of the PMN plasma membrane. Strongly increased activity at this site has been found in PMN from cancer patients. In most of them, additional staining has been observed in atypical vesicles and sometimes in the Golgi apparatus. These findings are discussed in the light of some previously reported controversial biochemical and cytochemical data on the distribution of alkaline phosphatase in human PMN.

Alkaline Phosphatase↗
PubMed1978

Purine nucleoside phosphorylase in chronic lymphocytic leukemia (CLL).

Purine nucleoside phosphorylase (PNP), the enzyme schematically next to adenosine deaminase in the purine salvage pathway, has been demonstrated cytochemically in peripheral blood lymphocytes of healthy subjects and chronic lymphocytic leukemia (CLL) patients. The enzyme activity is confined to the cytosol. In healthy subjects the majority of lymphocytes are strongly reactive for PNP, whereas the rest are devoid of cytochemically demonstrable activity. The percentage of PNP-positive cells largely corresponds to the number of E rosette-forming cells and is inversely proportional to the number of Ig-bearing cells. In six of seven CLL patients studied only a minor percentage of the lymphocytes showed strong PNP activity, whereas the large majority (88%--98%) possessed trace activity. Such patients have a high number of Ig-bearing cells and a low number of E rosette-forming cells. A different pattern of markers was found in the lymphocytes of the seventh CLL patient: 66% were strongly reactive for PNP, an important number formed E rosettes, and a minor percentage were Ig bearing. These data indicate that PNP can be useful as a "nonmembrane" marker in the differentiation of the B and T cell origin in CLL and deserves to be studied in other lymphoproliferative disorders.

Histocytochemistry↗
PubMed1977

Purine nucleoside phosphorylase, a possible histochemical marker for T-cells in man.

A procedure is described for the histochemical detection of purine nucleoside phosphorylase (PNP) activity in circulating lymphocytes of man. The number of PNP-positive cells, as evaluated on smears of Ficoll--Hypaque purified cells, correlated well with the number of E-rosette-forming cells of the same blood samples of healthy and diseased people with normal or abnormal numbers of E-rosettes. In healthy people, the number of PNP-positive cells was within the range of 70-80% of the total lymphocyte population, whilst the corresponding E-rosette-forming cells were scored between 60-75%. Patients with unusually low or high E-rosettes had equally low or high numbers of PNP-reactive cells. More substantial evidence for the presence of PNP activity in T-cells and not in B cells was gathered from experiments in which PNP activity and surface membrane immunoglobulins (SMIg) were simultaneously demonstrated on the same preparation. These results showed, on the one hand, that the bulk of lymphocytes that are reactive for PNP do not reveal SMIg and, on the other hand, that most Ig-bearing cells were unreactive for PNP.

Histocytochemistry↗
PubMed1977

Cytochemical localization of NADH oxidase in Candida albicans.

The application of a recently published technique to localize reduced nicotinamide adenine dinucleotide oxidase activity is described in glutaraldehyde-fixed Candida albicans. The reaction product appears as a finely granular precipitate on the mitochondrial cristae and on the central vacuolar membrane, and, if present, on the vacuolar contents. Fixation should be kept to a minimum and prolonged incubation times up to 2 hr are necessary to show these reactive sites. The reaction appears to be strongly substrate-dependent and not affected by cyanide. Exposure of C. albicans cells to the antimycotic miconazole resulted in a strong increase in reduced nicotinamide, adenine dinucleotide and oxidase activity. The hypothesis is put forward that this enzyme, together with peroxidative and catalatic enzymes, may be implicated in the mechanism by which miconazole exerts its lethal effect on C. albicans.

Candida albicans↗
PubMed1976

Further characterization of phosphatase activities using non-specific substrates.

The demonstration of non-lysosomal acid phosphatase has been the subject of a number of recent investigations. In the present study we compared the enzyme activities in rat liver and kidney that are revealed after incubation in the presence of either beta-glycerophosphate, p-nitrophenylphosphate or phenylphosphate at varying pH. As seen by others, the activity towards p-nitrophenylphosphate at pH 5-6 was confined to lysosomes, Golgi apparatus, endoplasmic reticulum (ER), nuclear envelope and plasmalemma. The reactivity of the plasmalemma and the ER was increased at pH 7. The TER of Küpffer cells in the liver stained intensely in contrast to the ER of the parenchymal cells, which stained only weakly. In the presence of NaF, all sites except the plasmalemma became negative. Addition of a levamisole-analogue, L-p-bromotetramisole, which is a specific inhibitor of alkaline phosphatase, resulted in the disappearance of the plasmalemmal activity whereas the activity at the other sites appeared unaltered. The rather unusual locations of activities with so-called non-specific substrates were further compared with those obtained with specific substrates such as glucose-6-phosphate and thiamine pyrophospate. The possible implication of these data in relation to the specificity of marker-enzymes for subcellular organelles is discussed.

Animals↗
PubMed1975

The inhibition of alkaline phosphatase by L-p-bromotetramisole.

A levamisole analogue, the L-p-bromotetramisole is introduced as a potent inhibitor of non-specific alkaline phosphatase. Complete inhibition is achieved cytochemically at a concentration of 0.1 mM in various rat tissues except the intestine, which is not affected. The D-p-bromotetramisole does not influence the alkaline phosphatase activities. Since no effect of the inhibitor is seen on the activities of specific phosphatases, this drug is recommended also as an additive for specific phosphatase media in order to yield the specific activity only.

Adenosine Triphosphatases↗
PubMed1975

The development of alkaline phosphatase in trichinous muscle.

The development of alkaline phosphatase during invasion and encystment of Trichinella spiralis in rat skeletal muscle fibres was studied at the ultrastructural level. On day 14 after infection, the enzymatic activity is found in proliferating parts of the T-tubular system and in parts of the plasmalemma. In cells, in which a strong hyperplasia of this system is noted. AlPase is present in the abundant network of stratified and concentric membranes from which a large number of pinocytic vesicles arise. From day 50 till 1 year after infection the enzyme activity was invariably present in the matrix surrounding the larvae and was confined to the enormous amounts of cytoplasmic membranes. The possible functional significance of this enzyme in the matrix, in view of its peculiar localization in the immediate vicinity of the parasite, is discussed. In the presence of 0.1 mM of the levamisole analogue, compound R 30402, which is a stereospecific inhibitor of AlPase, the activity is completely lost.

Alkaline Phosphatase↗
PubMed1975

Enzyme cytochemistry of Candida albicans.

The application of a new preparation method for demonstrating the activities of hydrolytic and oxidative enzymes in Candida albicans is reported. The problem of inadequate penetration of fixatives into yeast cells has been solved by sectioning solidified pellets of the cells in the presence of glutaraldehyde, a procedure that yields a fairly well preserved ultrastructure and sufficient enzyme activities. The subcellular distribution of most specific and nonspecific phosphatases and of peroxidases is at variance with that found in mammalian cells. The activities toward beta-glycerophosphate, p-nitrophenylphosphate, adenosine triphosphate, adenosine monophosphate, thiamine pyrophosphate and glucose 6-phosphate are almost exclusively confined to the central vacuolar apparatus. Oxidative and peroxidative activities are demonstrated only in mitochondria. Specific marker enzymes for endoplasmic reticulum, plasmalemma, Golgi apparatus and peroxisomes in C. albicans are not found. The possible function of the various subcellular organelles in relation to their enzymatic content is discussed.

Acid Phosphatase↗
PubMedDate not supplied

Chronic hibernating myocardium: interstitial changes.

Chronic left ventricular dysfunctional but viable myocardium of patients with chronic hibernation is characterized by structural changes, which consist of depletion of contractile elements, accumulation of glycogen, nuclear chromatin dispersion, depletion of sarcoplasmic reticulum and mitochondrial shape changes. These alterations are not reminiscent of degeneration but are interpreted as de-differentiation of the cardiomyocytes. The above mentioned changes are accompanied by a marked increase in the interstitial space. The present study describes qualitative and quantitative changes in the cellular and non-cellular compartments of the interstitial space. In chronic hibernating myocardial segments the increased extracellular matrix is filled with large amounts of type I collagen, type III collagen and fibronectin. An increase in the number of vimentin-positive cells (endothelial cells and fibroblasts) compared with normal myocardium is seen throughout the extracellular matrix. The increase in interstitial tissue is considered as one of the main determinants responsible for the lack of immediate recovery of contractile function after restoration of the blood flow to the affected myocardial segments of patients with chronic left ventricular dysfunction.

Actins↗
PubMedDate not supplied

Ultrastructural damage and Ca2(+)-shifts in the canine myocardium subjected to regional incomplete ischemia.

The role of Ca2+ in the pathogenesis leading to ischemic myocardial cell death is still controversial. To gain insight into this phenomenon a cytochemical procedure, the phosphate pyroantimonate method, was used to localize different subcellular Ca2(+)-pools at the ultrastructural level. After 45 min of left anterior descending coronary artery (LAD) occlusion, the coronary arteries were perfused with triphenyltetrazoliumchloride staining (TTC) to identify viable ischemic and infarcted tissue. In non-ischemic tissue, Ca2(+)-deposits were confined to the sarcolemma, sarcolemma-derived vesicles, transverse tubules, and intercalated disks. In infarcted tissue (TTC-negative), the sarcolemma lost its Ca2(+)-binding capacity and mitochondria were either overloaded with Ca2(+)-precipitate or they contained amorphous densities. In viable ischemic areas (determined with the TTC-technique) the sarcolemma was virtually devoid of Ca2(+)-deposits. Mitochondria in this area frequently showed clumping of the cristae, associated with an accumulation of Ca2(+)-precipitate in between the clustered cristae. The results of this study indicate that Ca2(+)-shifts occur in ischemic myocardial cells before the occurrence of other ultrastructural signs of irreversible injury which, therefore, narrows the possibility that Ca2(+)-overload is only a consequence of ischemic cell death.

Animals↗